A rolling cone cutter earth boring bit consists of a main bit body adapted to be connected to a rotary drill string. The bit includes individual rotatable cone cutters mounted on individual bearing pins extending from the main bit body. Bearing systems are provided between the cone cutters and the bearing pins to promote rotation of the cutters and means are provided on the outer surface of the cone cutters for disintegrating the earth formations as the bit and the cutters rotate. A sufficient supply of uncontaminated lubricant should be maintained proximate the bearing systems throughout the lifetime of the bit. Various forms of seals have been provided between the cone cutters and the bearing pins upon which they are mounted to retain lubricant and prevent contamination; however, the need for new sealing systems is as acute today as any time in the history of rock drilling.
A rolling cone cutter earth boring bit must operate under very severe conditions and the size and geometry of the bit is restricted by the operating characteristics. At the same time, a longer lifetime and improved performance is needed from the bit. In attempting to provide an improved bit, new and improved materials have been developed for the cutting structure of the cone cutters. They have provided a longer useful lifetime for the cone cutters. This has resulted in the sealing and bearing systems of the bit being often the first to fail during the drilling operation. Consequently, a need exists for new and improved sealing and bearing systems to extend the useful lifetime of the bit and to allow development of other elements that interact with the sealing and bearing systems. Various prior art sealing systems have been provided to maintain the bearing area free of harmful materials and retain lubricant. In attempting to provide new sealing systems, great care must be taken that the overall capacity of the bearing systems is not reduced.
In order to more fully appreciate the problems involved in providing new sealing systems for rolling cone earth boring bits, the following factors should be borne in mind. Relatively loose manufacturing tolerances inherently necessary in bit bearing assemblies create sealing problems that have not been satisfactorily solved. The required manufacturing tolerances preclude effective use of the many common shaft sealing methods due to the limited ability of shaft seals to accept loose radial fits while still maintaining an effective sealing condition. Many bits utilize face type seals. These are usually of the rubber coated Belleville spring urged type since this type consumes a minimum of space. This rubber coated spring has been only moderately successful because the rubber sealing element is subject to rapid deterioration both through friction heating and through abrasion from exposure to the very deleterious environment encountered in oil well or blast hole drilling operations. Face type seals have not provided the long life and sealing efficiency necessary for non-friction bearing bits. Tight fitting friction type bearings using shaft seals such as rubber O-rings have had a relatively high degree of success but only in areas where proper cooling, such as a circulating liquid, can be supplied to the bit exterior environment. Such seals tend to deteriorate rapidly if subjected to abrasive materials and heat. Tolerance requirements also present problems because of the tight fitting requirements. The bit bearings should be a maximum size to withstand the very heavy loads imposed while at the same time yielding to the hole size limitations specified by the user. A dilemma of adapting a maximum capacity bearing in a minimum of space is produced. This dilemma invariably leads to compromises which circumvent many of the well known requirements for proper assembly and use of high precision elements. This tolerance accumulation presents obstacles in providing an improved sealing system.